Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy with an overall 5-year survival rate of 6%. The molecular mechanisms that contribute to the biological aggressiveness of PDAC are being gradually elucidated, and the crucial role of high and low frequency driver mutations in PDAC is providing new insights into the complexity of this cancer. However, the widespread consequences of aberrant transforming growth factor-beta (TGF-beta) actions in PDAC in the context of the presence of oncogenic Kras and loss of function of the retinoblastoma protein are not well understood. In this proposal we will use a novel genetically engineered mouse model (GEM) of PDAC that we generated in which oncogenic Kras is combined with RB deletion. The resultant KRC mice rapidly develop pancreatic intraepithelial (PanIN) lesions that progress to PDAC within weeks after birth, and the pancreatic cancer cells in these cancers are highly proliferative. Based on our published data and preliminary results, the KRC mouse will allow us to test the hypothesis that aberrant TGF-beta signaling in PDAC synergizes with RB inactivation, leading to deleterious actions by TGF-beta, aberrant mitogenic signaling, and enhanced pancreatic cancer cell proliferation and cancer cell-stroma interactions. We will evaluate the effects of RB loss of function on TGF-beta signaling, assess the role of TGF-beta signaling in PDAC metastasis, and delineate the contributions of inflammatory cytokines and Wnt pathways to pancreatic cancer cell proliferation and stroma formation. To this end we will use cell lines established from KRC pancreata, use other novel GEMs of PDAC generated in our laboratory that exhibit a high incidence of metastases, conduct therapeutic interventions in these GEMs, and assess the role of these pathways in human PDAC. The proposed studies will advance our understanding of PDAC pathobiology in a high impact manner, and will point the way to novel therapies for suppressing cancer growth and metastasis.